A printed wiring board such as a probe card is well known. The probe card is utilized to examine a semiconductor wafer and an LSI (large-scale integrated circuit) chip package, for example. A semiconductor wafer or an LSI chip package is set on the probe card. A high temperature operation test such as a burn-in test, or a low temperature operation test such as screening is executed. The probe card is subjected to a thermal stress such as a change in the temperature, namely a heat cycle. The temperature is forced to change in a range set for the high temperature test or the low temperature test.
The LSI chip includes a silicon substrate, for example. Silicon has a relatively low coefficient of thermal expansion, so that the LSI chip is allowed to have a relatively low coefficient of thermal expansion. On the other hand, the core substrate of the probe card is made of carbon fiber cloth impregnated with a resin material, for example. The carbon fiber cloth serves to reduce the coefficient of thermal expansion of the core substrate. The coefficient of thermal expansion of the probe card can be equalized to that of the LSI chip. The electrically-conductive pads of the probe card can thus be prevented from shifting from the corresponding electrode pins of the LSI chip, respectively, for example.
Through holes are formed in the core substrate of the probe card. A cylindrical large-sized via having a large diameter is formed on the inner wall surface of the individual through hole. A filling material made of a resin material fills an inner space within the large-sized via. A small-diameter through hole is formed to penetrate through the filling material. A cylindrical small-sized via having a diameter smaller than that of the large-sized via is formed on the inner wall surface of the small-diameter through hole. A filling material fills an inner space within the small-sized via. The filling material serves to electrically insulate the small-sized via and the large-sized via from each other. The filling material is made of epoxy resin, for example.
The carbon fiber cloth of the core substrate is a woven or nonwoven cloth, for example. The carbon fiber cloth extends along the front and back surfaces of the core substrate. This results in significant restriction of the thermal expansion of the resin material occurring in the in-plane direction of the core substrate during the heat cycle test, for example. The thermal expansion of the resin material thus tends to cause an increase in the thickness of the core substrate. The thermal expansion induces cracks in the probe card. Such cracks may cause break of an electrically-conductive pattern.